Selecting records in a list view will trigger the display of UI elements
that will allow users to manage the selection and run actions on the
selected records.
Prior to this commit, this UI section was displayed within the
'additional actions' slot of the CP, but for UI consistency when
switching to/from mobile view (where the searchbar is usually hidden),
a new slot for 'selection-actions' is added to the control panel, in the
same place as the searchbar (indeed the searchbar is hidden when a
selection occurs, so sharing the same space seems like a good idea as it
avoids clipping/overflow issues)
Part-of: odoo/odoo#116641